The post-war "coupon election" of December 14 1918 marked the dawn of modern British electoral politics. It was the first time the United Kingdom voted on a single day, and an electorate which had tripled in size since 1910 marched to the polls after the Representation of the People Act introduced universal male suffrage and extended the vote to six million women.

The election was called only 24 hours after the cessation of hostilities on November 11, and was dominated by the collective experience of the first world war, and the daunting task of reconstruction. A war-weary electorate chose what they knew: a coalition government led by "The Man Who Won The War", David Lloyd George.

For the Liberals, dominant since their landslide victory in 1906, it was a disaster. Split into factions following rival leaders Lloyd George and Herbert Asquith, their principles challenged by the savageries and necessities of the war, and their progressive political territory challenged by a growing Labour movement, the 1918 campaign broke the back of the party: the Liberals would never again form their own government.

The Manchester Guardian was stunned by the scale of the coalition victory. "One hardly knows where to begin with an earthquake," it shuddered on December 30. "All the Liberal front Opposition bench has been swept out of Parliament ... The Labour party has increased its membership by about 50%, but it has lost most of its leadership and practically all of its able Parliamentarians."

Many historians blame Lloyd George for the Liberals' reversal of fortune, arguing that he deliberately failed to heal the schism in order to consolidate his ascendancy over the party's official leader, Herbert Asquith. He had served Asquith as chancellor, munitions minister and war secretary, but resigned from his government in 1916 in protest over the direction of the war. The military disasters of the Somme and Gallipoli, as well as the Easter Rising in Dublin, had been pinned on Asquith, who had been forced to resign. With the help of the Conservatives, Lloyd George took the helm of the coalition two days later.

Early in the 1918 campaign, Lloyd George's language had been conciliatory towards his former colleagues in Asquith's wing of the party. At a Downing Street press conference shortly after dissolving parliament, he declared that he remained true to the Liberal faith in free trade and peace, hinted at the introduction of a minimum wage at home, and pledged that peace with Germany would be negotiated on the Liberal principle of justice rather than revenge. Within days, however, he was calling to "make Germany pay", had turned on his previous colleagues, questioning their support for the coalition and introducing the fateful list of approved "coupon" candidates.

He handpicked 159 loyal Liberals to stand on a coalition ticket and marked them out to voters with the "coupon" - a letter he had co-signed with his Unionist chancellor, Andrew Bonar Law. For almost all of them, it proved a ticket to parliament, as they were unopposed by Unionist candidates. A handful of Labour and Independent candidates were also elected for the coalition.

Meanwhile Asquith's Liberal faction was routed - with the official party leader losing his own seat in East Fife - and was outpolled for the first time by the Labour party. Only 28 anti-coalition Liberals were returned to the Commons, while Labour saw 57 non-coalition MPs elected.

Most of all, coalition candidates were able to capitalise on the national mood of jingoism, which had always been a problematic concept for non-interventionist Liberals, whose pre-war principles had been compromised by press censorship and conscription, necessitated by the protracted conflict.

Lloyd George - the "Welsh Wizard" - had promised voters "a land fit for heroes to live in". His coalition manifesto declared: "The unity of the nation which has been the great secret of our strength in war must not be relaxed if the many anxious problems which the war has bequeathed to us are to be handled with the insight, courage, and promptitude which the times demand."

"We appeal, then, to every section of the electorate, without distinction of party, to support the Coalition government in the execution of a policy devised in the interests of no particular class or section, but, so far as our light serves us, for the furtherance of the general good."

Electors were won over by the promise of land for returning servicemen, increased production, legal equality between men and women and a settlement in Ireland - although Irish independence was ruled out, as was forcing Ulster under a self-rule government from Dublin. The Liberals had succeeded at the third attempt in passing an Irish home rule bill in 1914, but it had been suspended for the duration of the war.

Asquith could not compete with Lloyd George for rhetoric. "I am not bound (as none of us should be) to any cut-and-dried programme," he wrote in a first-person manifesto emphasising his decades of experience in parliament and his post-war aspirations.

"In every chapter of reconstruction, I should be prepared to adopt for myself, and to recommend to my friends, as an appropriate watchword the formula of a national minimum ... we ought not to be content until every British citizen - man, woman, and child - has in possession or within reach a standard of existence - physical, intellectual, moral, social - which makes life worth living, and not only does not block, but opens the road to its best and highest possibilities."

Labour, for its part, had appealed directly to the newly enfranchised returning soldiers and sailors, as well as "men and women workers at home". "A million good houses" were to be built by the state, a "comprehensive Public Health Act" introduced and "real public education, free and open to all" was promised. Above all, Labour campaigned for a unilateral end to military conscription, for nationalised public services and for universal suffrage.

Once in power, however, Lloyd George quickly became isolated in his governing coalition, which was dominated by its Conservative members - known at the time as Unionists due to their opposition to Irish nationalism and republicanism. Some believe that Lloyd George had simply given up on Liberalism: he is said to have observed to the press magnate Ridell in January 1918 that the Liberal party was a thing of the past that could not be resuscitated. He also became frustrated by the Unionists' opposition to Irish home rule - necessitating ever more "illiberal" coercive measures to contain Irish unrest - and by their opposition to his proposals for social reform at home.

The coalition Liberals, meanwhile, lacked an ideological base and increasingly became hostage to their dominant Unionist partners. Although he remained prime minister until 1922, Lloyd George was more successful in his pre-war era, when as Asquith's radical chancellor he had introduced state pensions, compulsory health and unemployment insurance and a land tax so controversial that it required the creation of the Parliament Act of 1911 to get it through the Lords.

In foreign policy, Lloyd George is most famous for his formative role in drawing up the 1919 Versailles treaty, which established the League of Nations and set out a war reparations settlement with Germany. Although the British prime minister is said to have exerted a moderating influence on the vengeful French leader, Georges Clemenceau, and the idealist US president, Woodrow Wilson, the harsh settlement thrashed out at the Paris peace conference was later judged to have annihilated German chances of post-war economic recovery and contributed to the eventual rise of Nazism.

Of course, the 20th century Liberal party would have faced formidable challenges even without the disastrous impact of the first world war. It would always have had to respond to the democratising voting reforms, which saw a highly organised Labour movement vie for the mass electorate in Europe's most industrialised nation. Votes for women, meanwhile, presented the Liberals with a challenge at the other end of the spectrum. Not all women received the vote in 1918. Only women of property aged over 30, as well as university graduates - in all estimated to number around six million - were trusted with the franchise. Older, propertied women were often conservative, rather than radical, in nature and so more likely to vote Unionist than Liberal. Out of 17 women who stood for parliament in 1918, many having been involved in the suffrage campaigns, only one was elected. Constance Markewicz refused to take up her Commons seat, however, in line with Sinn Féin party policy.

Indeed the 1918 election also proved a watershed in Ireland, with Sinn Féin sweeping the board and demolishing the moderate constitutionalist Irish Parliamentary party. The crop of 73 elected MPs would provide the party with its next generation of leaders, and the caucus with which to set up an unofficial parliament, the Dáil, in Dublin. The radicalisation of representative politics in Ireland, just two years after the unrest of the Easter Rising, deepened the crisis and was a substantial step along the road to partition in 1920.